To treat or coat something with silicon or a silicon-based substance.
Siliconized things are often made to be more slippery or water-resistant.
Examples:
The company siliconized the baking sheets to make them non-stick.
I need to siliconize the bathroom tiles to make them waterproof.
She siliconized the paper to make it shiny.
He siliconized his shoes to make them waterproof.
The entire city was siliconized to make it water-resistant.
I siliconized my phone to protect it from water damage.